Why is my ContentResolver batch operation only putting in 7 out of 21 entries?

Question

I have three fragments in a FragmentPagerAdapter, and each of them would fetch a list of frames/data from a server using Volley. This data would later be used to update the Fragment's RecyclerView Adapter as a Cursor.

    VolleyRestClientUtils.get(getString(R.string.PATH_SHOP), LOG_TAG, params, true, false, new JsonHttpResponseHandler() {
        public void onSuccess(JSONObject response) {
            Log.d(LOG_TAG, "request Response : " + response.toString());
            try {
                String status = response.getString("status");
                if (RestClientUtils.STATUS_OK.equals(status)) {
                    final JSONArray frames = response.getJSONArray("items");
                    Log.d(LOG_TAG, "request Response : " + frames.length());
                    if (frames != null && frames.length() > 0) {
                        new AsyncTask<Void, Void, Boolean>() {
                            @Override
                            protected Boolean doInBackground(Void... voids) {
                                List<ContentValues> listShopFrame = ShopFrame.fromJSONArray(frames, sort);
                                if (listShopFrame.size() > 0 && isActivityActive()) {
                                    ContentResolver cr = getActivity().getContentResolver();
                                    if (!isRequestMore) {
                                        cr.delete(ShopFrame.CONTENT_URI, ShopFrame.COLUMN_CATEGORY + "=?",
                                                new String[]{sort});
                                        paramSkip = frames.length();
                                    } else {
                                        paramSkip += frames.length();
                                    }

                                    ArrayList<ContentProviderOperation> operations = new ArrayList<>();
                                    String log = listShopFrame.size()+" ";
                                    for (int i = 0; i < listShopFrame.size(); i++) {
                                        operations.add(ContentProviderOperation
                                                .newInsert(ShopFrame.CONTENT_URI)
                                                .withValues(listShopFrame.get(i))
                                                .build());
                                        log += listShopFrame.get(i).toString()+"\n";
                                    }
                                    Log.i("loader_callback_"+sort, log);
                                    //cr.applyBatch(ShopFrame.CONTENT_AUTHORITY, operations);
                                    ContentValues[] opsAsArray = new ContentValues[listShopFrame.size()];
                                    listShopFrame.toArray(opsAsArray);
                                    cr.bulkInsert(ShopFrame.CONTENT_URI, opsAsArray);
                                    //return true;
                                }
                                return true;
                            }

                            @Override
                            protected void onPostExecute(Boolean result) {
                                dataRefreshed = true;
                                Log.i("loader_callback_"+sort, "response post execute");
                                if (result) {
                                    loadSucceed();
                                    PicMixApp.getInstance().setRefreshed(ShopFrameFragment.this.getClass().getName());
                                } else {
                                    loadFailed(null);
                                }
                            }
                        }.execute();
                    } else {
                        //TODO
                        //Handle error
                        loadFailed(getString(R.string.err_load_s, getString(R.string.frame)));
                    }
                } else if (VolleyRestClientUtils.STATUS_RESOURCE_NOT_FOUND.equals(status)) {
                    hasMore = false;
                    loadSucceed();
                } else {
                    loadFailed(getString(R.string.err_load_s, getString(R.string.frame)));
                }
            } catch (Exception e) {
                Log.e(LOG_TAG, "Exception:" + e.getMessage());
                loadFailed(getString(R.string.err_load_s, getString(R.string.frame)));
            }
        }

        @Override
        public void onJSONError(String responseString) {
            loadFailed(getString(R.string.err_load_s, getString(R.string.frame)));
        }

        @Override
        public void onFailure(String errMessage, int statusCode, Map<String, String> headers, byte[] responseBytes) {
            loadFailed(getString(R.string.err_load_s, getString(R.string.frame)));
        }
    });

Whereas loadSucceed() has this following code:

if (this.recyclerView != null) {
        final RecyclerView.Adapter adapter = recyclerView.getAdapter();
        if (adapter != null) {
            adapter.registerAdapterDataObserver(new RecyclerView.AdapterDataObserver() {
                @Override
                public void onChanged() {
                    super.onChanged();
                    Log.i(DefaultRecyclerFragment.this.getClass().getName(), "onChanged");
                    adapter.unregisterAdapterDataObserver(this);
                    isLoading = false;
                }

                public void onItemRangeRemoved(int positionStart, int itemCount) {
                    Log.i(DefaultRecyclerFragment.this.getClass().getName(), "onItemRangeRemoved:" + positionStart + ", itemcount:" + itemCount);
                    adapter.unregisterAdapterDataObserver(this);
                    isLoading = false;
                }
            });

            if (adapter instanceof CursorRecyclerAdapter && loadMoreView != null) {
                ((CursorRecyclerAdapter) adapter).removeFooter(loadMoreView);
            }
        }
    }

I've put the code to initialize the loader in the onResume() method of each fragment:

int id = 100+Integer.valueOf(sort);
Loader l = getLoaderManager().getLoader(id);
Log.i("loader_callback_"+sort, "success loading volley "+l);
if(l == null) {
    getLoaderManager().restartLoader(id, null, this);
}

My problem is that there seems to be some sort of race condition happening, that the currently viewed fragment's adapter seem to be updated twice, and sometimes thrice. The initial cursor fetched by the Fragment's Loader has 10 rows, sure, but after the update, most of the time it only has 7 of the 21 rows expected to be put in.

I thought all the ContentResolvers' operations are synchronous (can only be done one after another, not simultaneously). What's going on here?

EDIT: Should I just put the loader init code in the loadSuccess() callback?

EDIT2: I should note that these Fragments extend android.support.v4.app.Fragment, and I'm using the version 27.1.1 of the Support Library.